Abstract : The optimum propellant tank shapes were found to be a spherical LH2 tank and in a LF2 tank with bulkhead ratio of 1.2. Both tanks are constructed of aluminum. Tank mounted super-insulation affords slightly better performance than shroud mounted insulation. Screen start baskets were selected as superior to dielectrophoretic devices and positive expulsion devices for use in orienting the propellants during coast. Capacitance probes were selected as the propellant management mass sensors due to their superior accuracy and proven reliability. The selected pressurization system utilizes a pressurant 'bubble-up' concept, where the pressurizing medium, helium, is bubbled through the propellants during the pressurizing cycle. The results of these optimization studies were used as the basis of the selected configuration design described in Volume II.